Dietary carbohydrate and fat independently modulate disaccharidase activities in rat jejunum.

The role of carbohydrate and fat in diet-induced modifications of jejunal disaccharidase activities was evaluated with an isoenergic diet containing a nonmetabolizable sugar, alpha-methylglucoside. Rats previously fed a high fat, low starch diet or a high starch low fat diet were force-fed three times over 12 h isoenergic high fat diets with or without alpha-methylglucoside, or a low fat diet containing alpha-methylglucoside. Regardless of the previous diet fed, force-feeding the high fat, alpha-methylglucoside diet produced significantly greater sucrase and lactase activities in the upper jejunum than force-feeding the high fat diet without alpha-methylglucoside; comparable or only slightly greater sucrase and lactase activities were seen in the lower jejunum. The animals fed the low fat, alpha-methylglucoside diet exhibited significantly greater sucrase and lactase activities in the lower jejunum than did the rats fed the high fat, alpha-methylglucoside diet; a less marked difference (< 30%) was observed between these two groups for disaccharidase activities in the upper jejunum. The lower sucrase and lactase activities observed in the jejunum of animals force-fed the high fat diet after consuming the high starch, low fat diet were accompanied by greater trypsin activity in the lumen of the upper and lower jejunum, suggesting that proteolytic degradation of sucrase and lactase might be stimulated in rats fed the high fat diets. These results suggest that both dietary carbohydrate and dietary fat independently and by different mechanisms modulate jejunal disaccharidase activities.